1. Field of the Invention
The present invention is directed generally to a light weight alternator, and in particular, a permanent magnet-type alternator including a voltage regulator for regulating the voltage output of the permanent magnet-type alternator.
2. Field of the Related Art
Various alternators use wound stator and rotor assemblies in which an electromagnetic force is produced in and around the rotor windings by admitting current through the rotor windings. In such designs, as the magnetic field produced in the spinning rotor couples with the windings at the stator, current is induced in the stator windings. These alternators, however, require brushes or slip rings to maintain a closed circuit for admitting the current necessary in the rotor during rotation. Because the brushes or slip rings are mechanical connections, they are susceptible to wear and corrosion.
The use of permanent magnet alternators have been found to be advantageous since they do not require that current be supplied to the rotor. In other words, the field inherent to and produced by the magnetic material of the permanent magnet alternators induces current in the stator as the magnet poles move in respect to the stator windings. Because it is not required to supply current to the rotor, slip rings and brushes are not required.
While the use of permanent magnet alternators have proven successful for various applications, the prior art systems have several shortcomings. Generally, because the alternator generates excessive heat, internal fans are provided on the drive end to cool the windings and the rotor. This increases the weight of the alternator, and thus, makes it undesirable for use in an automotive or aerospace capacity where fuel efficiency is needed. Moreover, many systems require the attachment of individual magnets to the outer circumferential surface of the rotor, which may result in the failure of the alternator if by chance one or more magnets becomes detached from the rotor due to the high centrifugal forces that result from the rotation of the rotor at high rpm or faulty adhesion between the magnet and surface. Yet another problem associated with permanent magnet alternators is the difficulty associated with controlling the output voltage generated in the stator windings as will otherwise inherently occur when the alternator is driven at variable rotational velocities. These drawbacks of the prior art are especially problematic in the vehicular environment where low cost, high reliability and light weight are all important to achieving a commercially acceptable design.